Tumor Paint: A Chlorotoxin:Cy5.5 Bioconjugate for Intraoperative Visualization of Cancer Foci

Abstract

Toward the goal of developing an optical imaging contrast agent that will enable surgeons to intraoperatively distinguish cancer foci from adjacent normal tissue, we developed a chlorotoxin:Cy5.5 (CTX:Cy5.5) bioconjugate that emits near-IR fluorescent signal. The probe delineates malignant glioma, medulloblastoma, prostate cancer, intestinal cancer, and sarcoma from adjacent non-neoplastic tissue in mouse models. Metastatic cancer foci as small as a few hundred cells were detected in lymph channels. Specific binding to cancer cells is facilitated by matrix metalloproteinase-2 (MMP-2) as evidenced by reduction of CTX:Cy5.5 binding in vitro and in vivo by a pharmacologic blocker of MMP-2 and induction of CTX:Cy5.5 binding in MCF-7 cells following transfection with a plasmid encoding MMP-2. Mouse studies revealed that CTX:Cy5.5 has favorable biodistribution and toxicity profiles. These studies show that CTX:Cy5.5 has the potential to fundamentally improve intraoperative detection and resection of malignancies. [Cancer Res 2007;67(14):6882-8]

Fluorescent labeled anti‐EGFR antibody for identification of regional and distant metastasis in a preclinical xenograft model

“…Recent preclinical investigations have identified chlorotoxin labeled with Cy5.5 as a potential method for imaging brain tumors intraoperative to determine surgical margins. 3 However, unlike the current study, these authors and others 4 exploring optical contrast agents for clinical translation have used small animal imaging techniques (eg, the IVIS-100 system, eXplore Optix, Kodak in vivo imaging system) to demonstrate feasibility. However, these recent publications suggest a growing enthusiasm for optical imaging as an emerging technology with high clinical potential for surgeons.…”

“…However, these recent publications suggest a growing enthusiasm for optical imaging as an emerging technology with high clinical potential for surgeons. 3,4,[21][22][23][24] Several obstacles to optical imaging in a clinical setting do exist. Although cetuximab is FDA approved for use in humans, the fluorophore Cy5.5 is not.…”

“…3,4 The selective property of therapeutic antibodies for tumor cells makes this an optimal method for imaging. Epidermal growth factor receptor (EGFR) is overexpressed in 80% to 90% of head and neck cancers and is upregulated during the early stages of tumor development.…”

The use of fluorescent dyes and probes in surgical oncology

“…59 In phase I clinical trials for human brain cancer therapy TM-601, the synthetic version of chlorotoxin, was tested and no dose-limiting toxicities were observed. 60 Veiseh et al (2007) coupled CTX to Cy5.5 at doses used for optical imaging in several xenograft mice models without detecting any toxicity. 61 The effective use of fluorescent antibodies to visualize antigens was demonstrated already in 1995.…”

“…60 Veiseh et al (2007) coupled CTX to Cy5.5 at doses used for optical imaging in several xenograft mice models without detecting any toxicity. 61 The effective use of fluorescent antibodies to visualize antigens was demonstrated already in 1995. 62 Ballou et al conjugated several antibodies to cyanines in teratocarcinoma and melanoma mice.…”